This invention relates generally to poly(aryl ether ketones) bearing alkylated side chains. It relates particularly to soluble, thermally stable, low dielectric poly(aryl ether ketones) with alkylated side chains and especially to films and coatings thereof.
As a class, poly(aryl ether ketones) are thermoplastic matrix resins that exhibit high strength, toughness, good electrical properties, thermooxidative stability and solvent resistance. The insoluble nature of these polymers, however, prevents them from being solution cast into polymer films and necessitates that they be extruded instead. Insolubility is evidenced in Victrex""s PEEK(copyright), a commercially available poly(aryl ether ketone).
Fluorinated poly(phenylene ether ketone), 12-F-PEK, films and coatings incorporating hexafluoroisopropylidene have been synthesized that are thermally stable, low dielectric, highly transparent and soluble in common organic solvents thus enabling them to be solution cast or spray coated to produce thin films and coatings (U.S. Pat. No. 4,902,769). These polymers, however, are produced from fluorinate monomers that are expensive and environmentally unfriendly.
The present invention reduces the amount of fluorine added by way of replacing some of the fluorine groups with alkylated side chains. The resulting polymer has the desired properties of thermal stability, low dielectricity and solubility in organic solvents.
Accordingly, it is a primary object of the present invention to provide soluble, thermally stable, low dielectric poly(aryl ether ketones) with alkylated side chains.
It is further an object of the present invention to provide films and coatings thereof.
According to the present invention the foregoing objects are achieved by the provision of a poly(aryl ether ketone) having the following structural formula: 
wherein Y is selected from the group consisting of CF3 and CH3; and wherein R is CnH(2n+1) and n=11-18.
This polymer is prepared by reacting alkylated diphenols of the following structure 
where n=11-18;
with activated bisfluorophenyl monomers of the following structure 
where X is CF3 or CH3.
Random terpolymers were derived from the reaction of 2,2-bis(4-carboxyphenyl)hexafluoropropane (Bis-AF), and an alkylated diphenol, as shown above, with an activated bisfluorophenyl monomer, as shown above.
By the present invention, poly(aryl ether ketones) bearing alkylated side chains are provided which are soluble, thermally stable, low dielectric and can be solution cast or sprayed to produce films and coatings.
Poly(aryl ether ketones) were prepared according to the route shown below: 
The first step in preparing these poly(aryl ether ketones) involves synthesis of an alkylated diphenol. Any methyl ketone with at least eleven total carbon atoms could be condensed with phenol to yield the desired monomer. Addition of anhydrous hydrogen bromide and a sulfur-containing catalyst, such as mercaptoacetic acid, along with anhydrous hydrogen chloride could be used to produce the desired bisphenol. The modified bisphenol is shown below: 
where n=11-18.
The next step is to prepare the activated bisfluorophenyl monomer, as shown below: 
This compound, 6HDCA, and its fluorinated analog, 6FDCA, were reacted with thionyl chloride with DMF as a catalyst to produce the corresponding chloroformylphenyl compounds in good yields.
In the naming of the polymers, the C11 and C17 refer to the length of the carbon chain attached between the ether linkages, and the 6F refers to the hexafluoroisopropylidene group located between the ketone linkages. The polymers designated with an AF in the name indicate a random terpolymer made from Bis-AF and the alkylated bisphenol present in a one to one ratio (i.e. AF:C11(1:1)).
All the PEKs synthesized were soluble in common organic solvents such as chloroform and tetrahydrofuran as well as polar aprotic solvents, such as N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide. The inherent viscosities for the polymer series ranged from 0.56-1.04 dL/g, and all were measured at a concentration of 0.25 g/dL at 25xc2x0 C. in chloroform. All polymers precipitated as white fibrous materials. Yields for the polymers ranged from 80-93% with the lowest being for AF:C17-PEK. All elemental analyses were within 0.6% of theoretical. Clear, colorless, tough, creasable films were cast from chloroform (15%w/v). These films were use to determine dielectric constants as well as infrared spectra. All the PEKs were subjected to thermogravimetric analysis (TGA) in both air and nitrogen. Thermal stabilities, taken at a 10% weight loss with a heating rate of 20xc2x0 C./min., ranged from 402xc2x0 C.-479xc2x0 C. in air and 450xc2x0 C.-494xc2x0 C. in nitrogen. Char yield (%) were determined in nitrogen at 800xc2x0 C. and ranged from 30-50 percent. All the PEKs were also analyzed by differential scanning calorimetry (DSC) in nitrogen. Glass transition temperatures (Tg) were taken as the midpoint of the step transition during the second heating and ranged from 78xc2x0 C. for 6FC17 to 143xc2x0 C. for AF:C11 (1:1).